Tongbin Yu

A Reconfigurable Microstrip Antenna With Radiation Pattern Selectivity and Polarization Diversity

A novel reconfigurable microstrip antenna with radiation pattern selectivity and polarization diversity is presented in this letter. A four-way power divider made by three Wilkinson power dividers and interconnected with switches (currently copper strips for proof of concept) is designed to feed this antenna. By controlling the states of the switches, the antenna characteristics can be changed into two modes. When the four rectangular radiating patches are excited by four sources with equal amplitude and phase, a metamaterial antenna with conical beam and linear polarization (LP) is achieved, while four sources with equal amplitude but 90° phase difference for each adjacent output leads to a wideband antenna with broadside beam and circular polarization (CP). This single-port antenna is useful for terrestrial land-mobile or other wireless applications.

Multi-Frequency and Dual-Mode Patch Antenna Based on Electromagnetic Band-gap (EBG) Structure

Microstrip patch antenna with multi-frequency and dual-mode is presented in this communication. The introduction of metamaterial substrate made of modified mushroom-type electromagnetic band-gap (EBG) structure enables the multi- functions. The composite right/left-handed transmission line (CRLH TL) theory and multi-conductor transmission line (MTL) theory are introduced to analyze and design this kind of antenna. Three modes including one monopolar radiation pattern in the n=0 mode and two patch-like radiation patterns in the n=-1, 1 modes respectively are analyzed and can be tuned by the parameters of the EBG structure. Since geometry of the radiating patch does not affect the infinite wavelength mode, circular polarization (CP) is obtained for the n=+1 mode by truncating the square radiating patch with linear polarization (LP) for the n=0 mode staying unchanged. Thus dual polarized antenna is obtained. Two prototypes of probe-fed patch antennas are fabricated to verify the theory analysis.

Gain Enhancement for Broadband Periodic Endfire Antenna by Using Split-Ring Resonator Structures

A novel broadband high gain periodic endfire antenna is presented. Broad bandwidth is realized by using a parallel strip line (PSL) feed and bowtie dipole elements while gain enhancement is achieved by loading split-ring resonator (SRR) structure in the endfire direction. The measurements show that SRR-loaded antenna presents gain of about 6.2~9.9 dB in the whole working band (5.1~8.2 GHz), which is about 1.3~4.2 dB more than the unloaded one. This antenna can be used in wireless communication systems for its advantages of broad bandwidth and high gain.

Single-Feed Dual-Band Dual-Mode and Dual-Polarized Microstrip Antenna based on Metamaterial Structure

A novel single-feed dual-band dual-mode and dual-polarized microstrip antenna based on metamaterial structure is proposed. The composite right/left-handed transmission line (CRLH TL) theory is used to design this antenna. Dual-mode can be obtained by exciting the antenna with a monopolar radiation in the n = 0 mode and a patch-like radiation pattern in the n = +1 mode, respectively. As the geometry of the radiating patch does not affect the infinite wavelength mode, circular polarization (CP) is obtained for the n = +1 mode by truncating the square radiating patch with the n = 0 mode, linear polarization (LP) staying unchangeable. Results of a fabricated one illustrate that this antenna is valuable in practical application for its low-profile, easy fabrication, radiation pattern selectivity and polarized diversity.

Broadband High-Gain Periodic Endfire Antenna by Using I-Shaped Resonator (ISR) Structures

A broadband high-gain periodic endfire antenna is presented in this letter. The gain enhancement is achieved by loading with an I-shaped resonator (ISR) structure in the endfire direction. Parameter extraction for the I-shape unit-cell structure is investigated to analyze its effect on the gain enhancement value of the antenna. Finally, both the ISR-loaded antenna and unloaded one are fabricated to verify the predictions. The measurements show that the ISR-loaded antenna presents gain of about 6.5-9.5 dB in the whole working band (about 5.1-8.3 GHz), which is about 1.5-3.5 dB more than the unloaded one. The advantages of broad bandwidth and high gain make this antenna valuable in wireless communication systems.

A Low-Cost Compact Patch Antenna With Beam Steering Based on CSRR-Loaded Ground

A novel low-cost compact patch antenna with capability of beam steering is presented in this letter. The complementary split-ring resonators (CSRR)-loaded ground structure enables the property of wide-scale steering range and can greatly reduce the cost of a phased-array system to meet the requirement of the wireless communications. Parameter extraction for the CSRR structure is investigated to analyze the effect of the loading metamaterial on the radiation pattern of the antenna. It is shown that the refractive index of the loading part affects the beam direction. Both of the single and double CSRR-loaded antennas are fabricated to verify the design. Measured results show that the beam of the double CSRR-loaded antenna can scan from -51° to 48° via changing the parameters of CSRR structure.

Broadband C-Shaped Circularly Polarized Monopole Antenna

A novel broadband monopole antenna with circular polarization (CP) is designed and fabricated. It consists of a C-shaped monopole, an open-loop on the backside of the monopole and a modified ground plane. By placing a rectangular open-loop coplanar with the ground plane and connecting a rectangular vertical stub to the ground plane, wide impedance bandwidth is achieved, and axial-ratio (AR) bandwidth of the antenna could be improved simultaneously. The measured results exhibit a 65.2% (4.14 GHz, 4.28-8.42 GHz) CP bandwidth, and the 10-dB impedance bandwidth is 87.7% (6.66 GHz, 4.26-10.92 GHz). Finally, by placing a reflector underneath the antenna with its structural dimensions unchanged, one can obtain unidirectional radiation patterns with greatly improved gains. The advantages of the proposed antenna are the simple structure, a compact size, and a broad 3-dB AR bandwidth.

NOVEL PHASE-SHIFTING CHARACTERISTIC OF CRLH TL AND ITS APPLICATION IN THE DESIGN OF DUAL- BAND DUAL-MODE DUAL-POLARIZATION ANTENNA

The phase-shifting characteristic of a novel composite right/left handed transmission line (CRLH TL) for two frequency points is analyzed in this paper. Samples of (90 - , 0 - ) and (180 - , 0 - ) phase-shifting TLs for two frequency points (f1; f2) are deigned and the total length of the CRLH TLs has decreased by more than 77% compared to the conventional microstrip lines. Then a four way power divider made by three Wilkinson power dividers and interconnected with the (90 - , 0 - ) and (180 - , 0 - ) phase-shifting TLs is designed to feed an antenna with two difierent operating modes at two difierent frequency bands. Four radiating patches arranging symmetrically in a loop are printed in an upper substrate and connected with the four outputs of the feed network by four copper pins. When the four rectangular patches are excited by four sources with equal amplitude and phase at f1, metamaterial antenna with conical beam and linear polarization (LP) is achieved; while four sources with equal amplitude but 90 - phase difierence for each adjacent output at f2 leads to wideband antenna with broadside beam and circular polarization (CP). One antenna prototype with dual-band dual-mode dual-polarization property is fabricated and good agreements between simulation and measurement results are obtained. This single-feed patch antenna is valuable in wireless communications for its radiation pattern selectivity and polarization diversity.

A Single-Feed Broadband Circular Polarized Rectangular Microstrip Antenna With Chip-Resistor Loading

A single-feed circular polarized (CP) rectangular microstrip antenna (MPA) is proposed. Capacitive disk coupling feed is used in the design. By connecting a resistor load to another capacitive disk at the opposite position, CP radiation over a wide frequency range is realized. Experimental results show that the fabricated antenna has an impedance bandwidth (S11 return loss) of 78.7% and a 3-dB axial ratio (AR) bandwidth of 27.5%. The peak gain level is about 6.8 dB. As a result, this antenna can be used in occasions when wide AR CP performance is desired.

A Dual-Band Microstrip Antenna with Omnidirectional Circularly Polarized and Unidirectional Linearly Polarized Characteristics Based on Metamaterial Structure

A novel single-feed dual-band microstrip antenna with omnidirectional circularly polarized (CP) and unidirectional linearly polarized (LP) characteristics for each band is proposed in this paper. The function of dual-band dual-mode is realized based on loading modified mushroom structure. By employing curved branches in the radiating patch, CP property for the omnidirectional zeroth-order resonance (n = 0 mode) is achieved. As the curved branches have little effect on the radiation pattern of patch mode, LP property for n = +1 mode stays the same. A prototype is fabricated to verify the properties of the antenna. Both simulation and measurement results illustrate that this antenna is valuable in practical application for its low-profile, radiation pattern selectivity and polarization diversity.